Ultra high frequency electric discharge device



March 2,1948. S OTT'ETAL, 2,437,130

ULTRA HIGH FREQUENCY ELECTRIC DISCHARGE DEVICE Filed Oc't. 6,1944- /z Z :4 y

Inventors:

William J. Scott, C\flvfiscopi eir- \l-M'Hne Their Attprney Patented Mar. 2, 1948 UNITED STATES PATENT OFFICE- 2,437,120 ULTRA HIGH FREQUENCY ELECTRIC DISCHARGE DEVICE- William Scott and Christopher T Milner, ltugby, England, assignors to General Electric Company, a corporation of New York Application October 6, 1944, Serial No. 557,451

In Great Britain July 3, 1942 Section '1, Public Law 690, August s, 1946 Patent expires July 5, 1963 3 Claims.

This invention relates to ultra high frequency system's em'pmyi'ng an electron discharge oscillator having a cavity resonator and it has for its object to provide an improved arrangement for abstracting energy from such a resonator. I

This invention relates more particularly to an improved coupling of an output linetothe resonator of an electron discharge oscillator of the velocity modulation type empioymg an envelope wholly or partiyermeta and in which-the resenatorforms part er the bulb or can of the elec tron discharge device and the concentric output line has its outerconductor pa singthrou the stein or header closing one end of the envelope. In such a construction, the-end of the concentric line bears a loop which enters a, hole in the "resonato'r. Y

In such constructions as have hitherto been adopted, the termination of the outer conductor at the output line of the resonator has not been such a'sto exclude leakage of resonant power at the joint with resultant loss of efiic'iency.

The present invention consists in eliminatin all possibility of leakage of resonant frequency field between the end of "the outer conductor of the output concentric line and the resonator hole by providing an overlapping joint, not entering the resonator, between the outer conductor and the wall so that, when the header is assembled to the metal envelope, as by weldingth'e're is a relatively tight joint between the outer conductor and the resonator.

Further to improve this joint, a low melting point metal, such as tin, may be placed in or around 'the joint so that during eikhaust the tin melts and makes a soldered joint.

For a better understanding of the invention, reference may be had to the following description taken in connection with the accompanying drawing in which the single figure is a cross-sectional longitudinal view of an electric discharge device of the velocity modulation type built in accordance with the invention.

Referring particularly to the arrangement shown in the drawing, we have there illustrated the invention as applied to a reflex oscillator comprising an electron gun i, a cavity resonator or chamber 2. and a reflector electrode 3. The electron gun I, which comprises an emissive cathode surface 4 heated by a suitable filamentary heater 4 and is surrounded by an electrode 5 for suitably concentrating the electrons into a beam, is supported by lead-in conductors 6 and I which pass through glass-to-metal eyelet seals 8 in a metal header 9 which closes the lower end of the lower part II) ofthe envelope of the device. 'The upper wall ll of the part In forms a lower wall of the cavity resonator 2 which is completed by a flanged metal plate I2 secured to the wall II, as by welding, andwhich contains a centrally located apertur'e I 3 through which an electron beam from the electron gun 1 passes. A metallic tubular member I4 is secured to the upper wall II in alignment with the aperture [3 to define with the metal plate 12a narrow gap l5 in the cavity resonator 2 which is traversed by the electron beam projected from the g un I. Upon the metal plate I2 is, in turn, mounted a flanged plate l6 through an aperture in which is led by an eyelet seal I7 a lead=in wire l8 supporting the reflector electrode I In the operation of the electric discharge device of the velocity modulation type thus far described, the electron beam emanating from the gun I and accelerated by the anode or resonator structure 2 is velocity modulated periodically as it traverses the velocity modulating gap l5 by the variation in the electromagnetic fields thereacross, so that successive groups of electrons are alternately accelerated and decelerated, tending to group the electrons in the beam after thebeam has traversed the velocity modulation gap. After undergoing this velocity modulation, the electrons are reversed in direction of travel by the electrode 3 and re enter the cavity resonator delivering energy to the electromagnetic field thereof. Oscillations at the resonant frequency of the resowater 2 appear therein and are abstracted therefrom byan output lead which usually consists, in view of the ultra high frequency of such oscillations, of a concentric line IS, the inner conductor of the line terminating within the resonator 2 in a loop 28. The outer conductor 2| is secured at its lower end to the inside of the header 9 and is continued'exteriorly by an extension 22, the inner conductor passing through the header by way of a glass-to-metal eyelet seal 23. The free end of loop '20 is secured to the inner surface of outer conductor 2! at the point 20' inany suitable manner, such as by welding.

Leakage of radio frequency power may readily occur between the upper end of conductor 2| and the aperture 24 in the wall of cavity resonator 2 through which the loop 2!! extends. It is not generally possible to make an effective seal at this point when the wall portion [0 with its attached part is presented to the header 9 for sealing thereto. To avoid this difiiculty, according to the present invention, we eliminate all possibility of leakage of electromagnetic field between the end 3 of the conductor 2| and the wall H of resonator 2 by providing an overlapping joint, not entering the cavity, between the outer conductor 2| and the wall ll. As shown in the drawing, a flanged member or eyelet 25 is secured, as by welding,to

the lower surface of the resonator wall I I around the aperture 24 and, during assembly of the part l and header 9, the conductor 2| is inserted into the eyelet 25 so as to make a relatively close fit therewith. The joint may be further improved by placing a low melting point metal, such as a ring 26 of tin, in or around the joint so that, during the heating which accompanies the exhaust process, the tinmelts and forms a soldered joint. A tabulation 2'! depending from header '9 and communicating with an aperture 28 in that head er provides means whereby the device may be evacuated or exhausted.

Alternatively, the eylet 25 may be secured to conductor 2! and the butt joint between the eyelet and the resonator wall H formed during the assembly, The upper end of the conductor 2i may be flanged in place of providing a separate eyelet, the flange abutting against the resonator wall.

As a further alternative, the wall of the resonator may be downwardly flanged around the aperture 24 for'loop 26 and the conductor 2! inserted into the flange during assembly, If the cavity resonator is formed by producing a cavity in a relatively heavy block of metal and attaching a thin diaphragm in the cavity to completeit, as described in the copending applicationof William J.'Scott, Richard G. Saunders, and Robert Latham, Serial No. 557,452, filed October 6,1944, and assigned to the assignee of the present invention, an overlapping joint between conductor 2| and the thick wall of the cavity resonator is provided if the conductor 2! extends to and closely fits within the aperture 24 for the reception of the loop 28.

Although, in the drawing, practically the whole wall of the electric discharge device is shown as of metal, this construction is not essential. The leads supporting the electron gun may extend through a glass stem sealed to a glass portion which is, in turn, ring sealed to the wall portion l0.

While we have shown and described a particular'modification of our invention, it will be obvious to those skilled in the art that many changes and modifications may be made without departing from the invention and we thereforeaim in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What we claim as new and desire to secure by Letters Patent of the United States is:

I. An electron discharge device of the velocity modulation type having a cavity resonator integral therewith and a header terminating one end of said device, said resonator including a wall having an opening therein, a concentric output transmission line extending through said header and coupled to said resonator through said opening, said line having an outer conductor extending into proximity with said opening and a centrallydisposed inner conductor, said inner conductor extending into said resonator and having one end secured to said outer conductor whereby assembly of said device is facilitated, and means for preventing leakage of electro-magnetic fields between said outer conductor and said resonator comprising an annular flange surrounding said outer conductor and said opening in closely fitting relationship to said outer conductor and said wall.

2. An electron discharge device of the velocity modulation type having a cavity resonator integral therewith and a header terminating one end of said device, said resonator including a wall having an opening therein, a concentric output transmission line extending through said header and coupled to said resonator through said opening, said line having an outer conductor extending into proximity with said opening and a centrally disposed inner conductor, said inner conductor extending into said resonator and having one end secured to said outer conductor whereby assembly of said device is facilitated, and means for preventing leakage of electromagnetic fields between said outer conductor and said resonator comprising an annular flange external to said resonator surrounding said outer conductor and said opening in closely fitting relationship to said outer conductor and said wall.

3. An electron discharge deviceof the velocity modulation type comprising anenvelope for said device, a cavity resonator within said envelope, a header terminating one end of said envelope at a point spaced from said resonator, a concentric output transmission line comprising an outer conductor which passes through said header and an inner conductor which projects into said resonator, means for preventing the leakage of electromagnetic field between said outer conductor and said resonator, said means comprising a flange attached to said resonator and forming an overlapping joint with said outer conductor, said joint being wholly external to said resonator, and means sealing said joint comprising a low melting point metal disposed between said flange and said outer conductor.

WILLIAM J. SCOTT. CHRISTOPHER J. MILNER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,216,170 George Oct. 1, 1940 2,287,845 Varian et a1 June 30, 1942 2,304,186 Litton Dec. 8, 1942 2,309,966 Litton Feb, 2, 1943 

